Is there a way to pick multiple mask fills to a slider?

Is there a way to pick multiple mask fills to a slider? My objective is to have multiple objects (for which I'm using masks) change color at a certain time, and it would be great if I could pick it to a slider to control the key frames.

but you can do one layer, then select that property and choose edit>copy expression only, then select all the layers that you want to have the same expression and paste. then they'll all be linked to the same control.

also,i think i'd link the color to a color control, then keyframe the color changes for the color control/color property, but i may not know exactly what you are trying to do....